Bending apparatus

ABSTRACT

A bending apparatus for bending sheets consists of a punch and a cooperating die provided with a longitudinally extending recess in its surface turned towards the punch; at the bottom of the recess a stop bar is provided with which the spacing between the bottom and the top of the die recess is adjustable.

United States Patent Hanni et al.

[111 3,844,156 Oct. 29, 1974 BENDING APPARATUS Inventors: Eduard Hanni, Zofingen/Cl-l;

Walter Gygli, Niederbipp/CH, both of Switzerland Hammerle AG Maschinenfabrik, Zonfingen, Switzerland Filed: Apr. 2, 1973 Appl. No.: 347,043

Assignee:

Foreign Application Priority Data Apr. 13, 1972 Switzerland 3188/72 US. Cl 72/389, 72/448, 72/473 Int. Cl B21d 7/06 Field of Search 72/389, 448, 413, 473,

References Cited UNITED STATES PATENTS 7/1906 Horton 72/448 2,199,864 5/1940 Wehr 72/448 2,415,931 2/1947 Bratz 72/448 2,826,947 3/1958 Creek 72/448 3,146,819 9/1964 Van Endert 72/389 3,675,463 7/1972 Munschauer 72/448 Primary Examiner-C. W. Lanham Assistant Examiner-Gene P. Crosby Attorney, Agent, or FirmAbraham A. Saffitz [57] ABSTRACT and the top of the die recess is adjustable.

4 Claims, 3 Drawing Figures l BENDING APPARATUS The present invention concerns bending apparatus for bending sheet metal and consists of a bending bar or punch adapted to cooperate with a bending die which is provided with a longitudinally extending recess on its surface turned towards the bending bar or punch.

For bending sheet metal plates with the aid of bending apparatus as just described, there are basically two different known processes. The first process consists in using a punch having working edges which are at a mutual angle corresponding to the angle to be formed in the sheet. The die cooperating with such a punch has a recess which is V-shaped in section, wherein the angle included between the two flanks of recess again corresppnds to the angle to be achieved. The advantage of this bending apparatus is that a very accurate angle, within the smallest tolerances, may be realized without deviations in the sheet thickness or imprecisions in the movement of the punch being able to influence the size of the angle being formed. As a disadvantage one must state in the first place that with this tool only a definite angle can be formed, i.e., for each different angle a separate tool pair must be provided.

The second process consists in the so-called free bending of the sheet. To this end a bending bar or punch is used the working surfaces of which are at a mutual angle considerably smaller than the smallest angle to be formed. The die cooperating with such a punch has, again, a recess in its surface turned to the punch with a cross-section which may in principle be of any desired shape. Often a very narrow and deep V or U-shape is chosen for the cross-section. In free bending, the sheet to be bent lies in engagement on one side thereof along two lines or edges on the die and on the other side thereof along a line or edge on the punch. The angle to which the sheet is bent essentially depends only on the amount of movement of the punch. The further the punch enters into the die recess, the sharper is the angle formed in the sheet. The advantage of this type of bending is obvious: with the same tool pair different angles may be obtained. The disadvantage that must be accepted consists in that the angle formed is dependent on the sheet thickness. Particularly for thin sheets, the actual sheet thickness may significantly deviate from the nominal thickness, which inevitably leads to undesirable tolerances in the resulting angle.

It is the aim of the present invention to propose bending apparatus of the kind mentioned above, which is suitable for the free bending of sheets, at the same time combines the advantages of both bending methods and does not have their drawbacks. According to the inventiorr, the apparatus is characterized in that at the bottom of the die recess a stop member is provided with which the spacing of the bottom of the die from the top surface of the die is adjustable.

According to a first embodiment the stop member is formed as a readily removable and replaceable insert, whereby advantageously a set of stop members of differing thicknesses are available for selectable insertion into the die.

Another preferred embodiment consists in mounting a stop member the height of which is adjustable. This may e.g., be realized by providing the bottom surface of the die recess along its whole length with a number of mutually adjacently arranged oblique flat surfaces,

with the underside of the stop member having a corresponding number of complementary bevelled faces, somewhat in the manner of meshing sawteeth. In this case the stop member is arranged for displacement along the bottom of the die and may be connected with an actuator for displacing the member. Finally, a switch for limiting the movement of the punch may be provided in the die which switch is responsive to the pressure exerted on the stop member when in excess of a preadjustable pressure.

Preferred embodiments of the invention will be de scribed in detail in the following, with reference to the accompanying diagrammatic drawings, wherein:

FIG. 1 is a transverse section through a flrst embodiment of the application according to the invention,

FIG. 2 is a transverse section through a second embodiment, and

FIG. 3 is a longitudinal section along the line A-A in FIG. 2.

In FIG. 1 the punch is designated 1 and is secured to a carrier (not shown) or like support of a folding or bending press. Its two working surfaces 2 and 3 intersect at a tip or working edge 4 at an angle which is smaller than the smallest angle it is desired to produce. A die 5 cooperates with the punch I and is arranged on a work table, not shown, of a nonillustrated folding or bending press. The die 5 has a surface 6 which is turned towards the punch 1, and in which a recess 7 is formed; in the present example the recess 7 is rectangular in cross-section. At the bottom of the recess 7 a stop bar 8 is inserted and extends over the whole length of the die 5.

As can be seen clearly from the drawing, a sheet 9 to be bent lies against the tool pair 1 and 5 at three places, viz. along lines or edges a and b which are the edges of the recess 7 at the surface of the die and at the line c which is constituted by the working edge 4 of the punch. During the bending process i.e., by pressing the punch in the direction of the arrow, the engagement line 0 penetrates ever farther into the recess 7 until the angle of the sheet formed by the bending reaches the stop bar 8. In the die 5, a non-illustrated pressure switch is built-in which at that moment, i.e., on contact between the sheet 9 and the stop bar 8, interrupts the movement of the punch l. The angle formed in the sheet 9 is then defined by the opposite positions of the lines a and b, on the one hand, and the contact line of the sheet 9 with the stop bar 8 on the other hand, which latter of course lies on the surface of the stop bar 8. Thus the angle is independent of the sheet thickness because all three contact lines determining the angle lie on the same side of the sheet.

The stop bar 8 is secured by non-illustrated means to the die 5 in a readily detachable manner. To bend another angle with the same punch l and the same die 5 the stop bar 8 has to be replaced by another stop bar of different size.

Another embodiment variant is shown in FIG. 2. The punch is again designated with l and the die with 5. At the bottom of the recess 7 in the die 5 a stop bar 10 is positioned which has a height adjustable relative to the top surface of the die. This adjustability may be achieved, in a non-illustrated embodiment, by a plurality of spindles which carry the stop bar 10 and which are easily adjustable by a hand wheel.

A more elegant solution is shown, however, in FIG. 3. Here the bottom of the recess 7 is provided with a number of oblique flat surfaces 11 arranged behind one another, somewhat in the manner of sawteeth. The underside of the stop bar has correspondingly formed bevelled surfaces 12 while its top surface is plane and runs parallel to the top surface of the die. By displacing or reciprocating the stop bar 10 in the direction of the arrows the spacing between the surfaces of the stop bar 10 and the die is varied. Since this spacing defines an angle to be formed in the sheet, in this way a simple means of adjustability of the die is provided for the most widely varying angles. Expediently, the stop bar 10 may be connected with an actuating mechanism (not shown) which is controlled by a control device (also not shown). Thus it becomes possible to carry out, without changing the punch, successive operations on a sheet to obtain different angles.

With the proposed bending apparatus very rational and precise working is rendered possible since no work tool needs to be replaced when the bending angle changes, and since unavoidable size tolerances of the sheet have no influence on the size of the bending angle obtained.

We claim as our invention:

1. Bending apparatus for bending sheets, comprising a punch and a cooperating die, a longitudinally extending recess in the surface of the die turned toward the punch, a stop member disposed in the bottom of the recess and having bottom and top surfaces, and means for changing said stop member to provide a different spacing between said bottom and top surfaces in the die re-. cess, whereby, the degree of bending can be varied by changing said spacing of the stop member.

2. Bending apparatus according to claim 1 wherein the stop member has predetermined dimensions, is formed as a readily removable and replaceable insert, and forms part of a set of similar but differently dimensioned inserts.

3. Bending apparatus according to claim 1 wherein means are provided for adjusting the height of said stop member.

4.Bending apparatus according to claim 3 wherein substantially the whole length of the bottom surface of the recess in the die is provided with a number of sawteeth-like oblique flat surfaces and there are, for cooperation with said flat surfaces, corresponding bevelled surfaces on the bottom of the stop member, said pair of surfaces constituting the means for adjusting the height of the stop member. 

1. Bending apparatus for bending sheets, comprising a punch and a cooperating die, a longitudinally extending recess in the surface of the die turned toward the punch, a stop member disposed in the bottom of the recess and having bottom and top surfaces, and means for changing said stop member to provide a different spacing between said bottom and top surfaces in the die recess, whereby, the degree of bending can be varied by changing said spacing of the stop member.
 2. Bending apparatus according to claim 1 wherein the stop member has predetermined dimensions, is formed as a readily removable and replaceable insert, and forms part of a set of similar but differently dimensioned inserts.
 3. Bending apparatus according to claim 1 wherein means are provided for adjusting the height of said stop member.
 4. Bending apparatus according to claim 3 wherein substantially the whole length of the bottom surface of the recess in the die is provided with a number of sawteeth-like oblique flat surfaces and there are, for cooperation with said flat surfaces, corresponding bevelled surfaces on the bottom of the stop member, said pair of surfaces constituting the means for adjusting the height of the stop member. 